The following description of background art may include insights, discoveries, understandings or disclosures, or associations together with disclosures not known to the relevant art prior to the present invention but provided by the invention. Some of such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context.
Radio-frequency filters are typically used in the base stations of mobile telecommunication networks, mobile phones and other radio transceivers. Possible radio-frequency filter applications include the adapter circuits and filter circuits of transmitter and receiver amplifiers.
In base station transmitter and receiver side filters, high Q cavity resonators are typically used. Good radio frequency properties such as low insertion loss and good power handling and a small size are especially required of radio-frequency filters. One typical solution is to use dielectric dual or multimode resonators. However, the realisation of such resonators is not an easy task.
At present, compact tranverse magnetic, TM, dual or single mode cavity resonators need ground contact or full metal plating around the ceramics. A joint between ceramic and metal is difficult to create because of different coefficient of linear temperature expansion. Besides, plating is needed on the ceramic for solder joint. When a fully plated ceramic block is used it is often difficult to connect it to other mechanics and get tunable couplings and frequencies.
There exist some orthogonal TM dual mode/multimode resonators without a straight cavity contact. However, they don't support a wide enough frequency band and they cannot be tuned from one side with good enough spurious response.